In my study on the McCann case I have found I couldn't rule out the possibility that someone else was aware that Madeleine had wandered out of the apartment prior to Kate's check.
There was the reports from Stephen Carpenter that his wife had mentioned someone calling "Madeleine" and this seems to be prior to 22.00.
If this person began looking for Madeleine prior to Kate's check then the lady, picking up her child from the night creche spoke to a man who was a Mark Warner guest, could have been informed about Maddie , Abby or Gabby, prior to Kate's check also. This scenario allows the three night creche workers to start heading toward the McCann apartment possibly at a time while Kate is still doing her check.
This scenario allows Amy to be in the apartment early enough to see the window open and shutter up, and for Charlotte to say she was in the apartment within 5 minutes of Madeleine being found missing by Kate.
The concept that some other Mark Warner guest was aware of Madeleine going missing prior to Kate's check needs investigating.